What is the purpose of the spark plug in a four-stroke engine?

The spark plug plays a crucial role in the operation of a four-stroke engine by providing ignition to the air/fuel mixture at the optimal moment. This ignition process is essential for initiating the combustion cycle, which ultimately produces the power that drives the engine’s pistons.

When the engine’s piston moves up during the compression stroke, the spark plug creates a small spark that ignites the compressed air/fuel mixture. This ignited mixture rapidly expands and generates high pressure, forcing the piston down during the power stroke. The timing of this spark is critical; if it occurs too early or too late, it can lead to inefficient combustion, potentially causing knocking or reducing engine performance.

Thus, the spark plug’s primary function is to ensure that the ignition of the air/fuel mixture happens at the precisely calculated moment to maximize engine performance and efficiency. This highlights the importance of regular spark plug maintenance and replacement to ensure consistent ignition timing and engine operation.